Modeling multi-cell IEEE 802.11 WLANs with application to channel assignment

We provide a simple and accurate analytical model for multi-cell IEEE 802.11 WLANs. Our model applies if the cell radius, R, is much smaller than the carrier sensing range, R_cs. We argue that, the condition R_cs >> R is likely to hold in a dense deployment of access points (APs). We develop a scalable cell level model for such WLANs with saturated nodes as well as for TCP-controlled long file downloads. The accuracy of our model is demonstrated by comparison with ns-2 simulations. Based on the insights provided by our analytical model, we propose a simple channel assignment algorithm which provides static assignments that are Nash equilibria in pure strategies for the objective of maximizing normalized network throughput, and requires only as many steps as there are channels. Furthermore, our channel assignment algorithm does not require any a priori knowledge of topology and can be implemented in a decentralized manner. In contrast to prior work, our approach to channel assignment is based on the throughput metric.